1. Field of the Invention
The present invention relates generally to an object or vehicle monitoring system and, more particularly, but not by way of limitation, to a quantized hyperbolic or inverse hyperbolic object or vehicle location system.
2. Brief Description of the Prior Art
In the past, various systems have been developed for identifying the location of objects such as ships, automobiles or vehicles, for example.
One such prior art system, utilized signpost units. In this type of signpost system, the signpost units were located at various predetermined geographic locations within a monitored area and each signpost unit transmitted a signal encoded with a predetermined signpost code which uniquely identified the particular signpost unit or, in other words, which uniquely identified the location of the particular signpost unit, thereby identifying the geographic location of the vehicle. The signpost unit output signals were received by vehicles traveling within the monitored area and the signpost code encoded in the received signpost unit output signal was utilized to determine the geographic location of the object. Although the signpost system was reliable and accurate, the signpost system did not have the disadvantage of requiring a number of electronic signpost units to be installed at known locations within the monitored area, thereby presenting manufacturing, maintenance and replacement problems and costs.
One other prior art system, utilized signals transmitted by three transmit stations when the signals were received via the object and the location of the object was determined via triangulation techniques. Various location errors have been associated with such triangulation techniques, such location errors being caused by deviations in the radio wave propagation due to inhomogeneous material or loss of signal by the object or vehicle receiver, for example. In connection with this prior art triangulation technique, a number of methods have been developed to correct the location errors, such as the use of signpost units located in signal loss regions and field calibrations used with computer prediction algorithms to correct radio wave propagation related errors. However, the correction methods required knowledge of where the erroneous radio signals were located. Thus, such correcting methods involved considerable costs in attempting to locate all such erroneous signal regions.